This invention relates to the art of edge bonding of metal strips and more particularly to a method for solid-phase edge bonding of metal strips.
There is considerable need for bonding dissimilar metals edge-to-edge. While the most practical method for edge bonding to date has been the use of electron beam welding, this technique has a number of drawbacks. The principal disadvantage is that electron beam welding creates a small but distinctive weld zone, composed of an alloy of the two metals being welded and a heat-affected area adjacent either side of the alloy. The weld zone is typically the weak link so that, under a tensile load perpendicular to the weld, the composite will usually fail at the weld zone rather than at one of the parent metals. Furthermore, the weld zone possesses characteristics dissimilar to those of the parent metals. These dissimilarities force design engineers to avoid this region and, therefore, incur increased costs due to increased metal consumption. Additional problems include sputter or blow holes in the weld zone, undercut (i.e., lack of weld penetration through the thickness of the composite), camber, and, because the metals are usually welded close to the finish gauge, relatively high production costs.
Another method for edge bonding uses electric resistance welding wherein high levels of electric current are applied to heat the edges of the metal strips to bond the same together. In U.S. Pat. No. 3,811,028 to Henry et al., a method of making a composite edgelay thermostat strip is described in which the two metal rods of hexagonal cross section are bonded by electric resistance welding while applying pressure, the composite is then heated or sintered to assure a complete metallurgical bonding, and the composite is then passed through rollers to reduce the thickness of the composite. In U.S. Pat. No. 3,737,979 to Rakich et al., a composite flat metal strip having portions of different thicknesses is produced by electric welding strips of different thicknesses along adjacent edges and by rolling the composite welded strip between male/female rollers of stepped cross section. In U.S. Pat. No. 3,325,623 to Briggs III, overhanging edges are edge-heated by electric welding to plastic temperature while lateral pressure is applied by rollers and the composite is then rolled to compress the upset bead at the weld.
Another method of making a composite edgelay material is described in U.S. Pat. No. 4,354,301 to Takeuchi et al. In Takeuchi et al., a plurality of metal sheets are bonded in a layer structure, cut into narrow multiple layer strips, turned 90.degree., and cold-rolled. The strips are then placed in a complimentary-shaped groove for maintaining the width of the strip while hot-rolling to extend in length.
Another method of bonding is described in U.S. Pat. No. 352,947 to Felt. Felt describes a process for manufacturing iron plates, shafts and axle-bars from scrap iron. The scrap articles are arranged in parallel, bound together by wrapping wires, heated, and then hammered or rolled to weld the separate articles together and reduce the same into a long bar or plate. The bars thus produced may be used for small shafts but are preferably combined with additional such layers and hammered together to the proper dimensions.
Methods for solid-phase bonding a pair of strips around a rod are disclosed in U.S. Pat. Nos. 4,227,061 to Westfall et al. and 3,714,701 to Dion et al.
It is an object of the present invention to provide a method for making an edge-bonded composite from a plurality of dissimilar metal strips by solid-phase edge bonding.
Another object is to produce such an edge-bonded composite wherein the bond is substantially as strong as the parent strips.
A still further object is to produce such an edge-bonded composite in a cost-efficient manner, including efficient use of the metal materials and low energy consumption.